Because it is dangerous for a driver to make a phone call by holding his mobile phone by hand during driving of an automobile, the driver sometimes uses a hands-free device to make a phone call from his mobile phone in the automobile. There are several connection systems between a hands-free device and a mobile phone, including a wired system and a wireless system. Particularly, a Bluetooth® wireless connection system is practically used and widely spread. For example, in-vehicle devices in which incorporates a hand-free function such as a hands-free head set and a car navigation system are practically used. A user connects his mobile phone to a head set or an in-vehicle device through Bluetooth® so as to make a hands-free call without holding his mobile phone while driving an automobile.
Bluetooth® is a near-field wireless-communication technique standardized by international standardization societies. Accordingly, a large number of mobile phones supporting Bluetooth® hands-free profiles exist in the world. For example, such a mobile phone is disclosed in Patent Document 1 mentioned below.    Patent Document 1: International Publication No. WO 03/061205 pamphlet